One would think there should be an abundance of axions everywhere in the Universe, even in our Solar system.
The mass of one axion is thought to be only of order 10^11 times the electron mass.
That's a LOT of axions where they may account for the dark matter.
There are probably more of them in certain regions but anyway...
So why try to detect them perhaps several lightyears from here?
And there are already ongoing experiments.
https://en.wikipedia.org/wiki/Axion#Experiments

Physics World is scarcely a 'tabloid' publication. It's distributed to members of one of the largest physical societies in the world.

A region of dark matter, called a caustic ring, may be quite near to us in space, enabling informative echoes from a microwave beam sent out from Earth to be returned in a reasonable length of time.

The proposed experiment would not be easy to set up, but could yield important new scientific data about dark matter and the structure of the universe. Noteworthy accomplishments in science require forward thinking like this, and, often, great effort.

I went back and it talks about the caustic ring as being part of the galactic halo, not near at all.

So I looked up caustic rings https://arxiv.org/pdf/astro-ph/9705038.pdf

In this case the Milky Way caustic rings are at the radii: 41, 20,13, 10, 8.0, 6.7, 5.8, 5.1, 4.5, 4.0, 3.7, 3.4, 3.1 ... kpc

A kpc kiloparsec is approximately 3262 light-years so possibly an experiment thousands of years long consuming MWyears of power or build a small nuke power plant just to run the experiment.

Perhaps not a tabloid publication but a tabloid article.

The paper linked above is over 20 years old. More recent work indicates that there appears to be a caustic ring much nearer Earth. I don't believe that a reputable journal, like Physics World, would publish a sensationalistic or misleading paper. I think it unfortunate to suggest otherwise, without a very substantial basis for doing so.

The paper linked above is over 20 years old. More recent work indicates that there appears to be a caustic ring much nearer Earth. I don't believe that a reputable journal, like Physics World, would publish a sensationalistic or misleading paper. I think it unfortunate to suggest otherwise, without a very substantial basis for doing so.

Michael, I was testing your knowledge, and you fail. Look up the distance of the sun from the Galactic center. Compare with the distances of these hypothetical caustic rings from that 20 year old paper. Then realize that the hypothesis of the caustic ring locations in the Milky Way is extrapolated from a single datum. If there are other papers that have looked at other galactic rotation curves and found caustic rings as a solution, they did not come up in my search. In any case the article's author didn't list a single cite in what you linked.

It isn't bad science, it is tabloid science a/k/a I published a paper this year, give me salary for next year.


BTW there are several papers out there indicating pressure waves as a likely source for the differences in density of the galactic medium.

If axions do exist and make up most of dark matter, their mass should be within the region of 50 to 1,500 microelectronvolts (μeV/c2) – up to ten billion times lighter than the electron (~0.51MeV/c2).
Using this estimate, every cubic centimetre of the universe contains 10 million of these super light-weight particles on average when it's only about 2 atoms in the same space on average.
But because dark matter is kept in clumps that form web-like structures, the local region of the Milky Way should have about one trillion axions per cubic centimetre.
But that's not by far enough to make up to the total mass of Dark Matter.
Perhaps they are in "Dark Stars", bizarre, star-like objects that act like single, giant atoms, as some suggests.
https://www.livescience.com/63977-axion-stars-form-quickly.html
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.151301

Dark matter secrets could lie buried in ancient rocks on Earth
https://www.newscientist.com/article/mg24132200-100-dark-matter-secrets-could-lie-buried-in-ancient-rocks-on-earth/

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Are Dark Matter And Dark Energy The Same?
According to some scientists it is but then you have to include negative mass particles...
https://www.youtube.com/watch?v=miGddxrvmDU

Jamie Farnes, astrophysicist at Oxford just published a paper suggesting that both dark energy and dark matter may result from the same phenomenon. And it’s pretty wild: negative mass particles continuously popping into existence between the galaxies. This rather extravagant claim resulted in a hysterical response from the media. Our viewers’ perfect blend of bright-eyed curiosity and cynical skepticism led to many MANY requests for us to do an episode on this new result. You got it. Today on Space Time Journal Club, let’s pick apart J.S. Farnes 2018, “A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified Lambda-CDM framework”.